ResultType.swift

enum Result<Value, Error: Swift.Error> {
    case success(Value)
    case failure(Error)
}

enum ApiError: Error {
    case none
    var desc: String {
        return "this is desc"
    }
}

func getSomethingFromServer(needValue: Bool) -> Result<Bool, ApiError> {
    switch needValue {
    case true:
        return .success(true)
    case false:
        return .failure(ApiError.none)
    }
}

let temp = getSomethingFromServer(needValue: true)
switch temp {
case .success(let value):
    print("Success \(value)")
case .failure(let err):
    print(err.desc)
}